Ionic vs. Molecular 1
Name ______________________________________________ Date _________ Period ______
Properties of Ionic and Molecular Compounds
Purpose
After reading the lab, create your own purpose below:
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Pre-Lab Discussion (Do not copy in your lab book)
Chemical compounds are combinations of atoms held together by chemical bonds. These
chemical bonds are of two basic types: ionic and covalent. Ionic bonds result when one or more
electrons from one atom or group of atoms are transferred to another atom or group of atoms.
Positive and negative ions are created through the transfer. In molecular compounds, which
contain covalent bonds, no electrons are transferred; instead electrons are shared by the bonded
atoms.
The physical properties of a substance, such as melting point, solubility, and conductivity,
can be used to predict the type of bond that holds together the atoms of the compound. In this
experiment, you will test six compounds to determine these properties. Your compiled data will
enable you to classify the substances as either ionic or covalent compounds.
Materials
Aluminum Pans
Conductivity Tester
Ethanol
Hot Glove
Hot Plate
Water Bottle
Well Plate
Calcium Chloride (CaCl2)
Citric Acid
Phenyl Salicylate
Potassium Iodide (KI)
Sodium Chloride (NaCl)
Sucrose (C12H22O11)
Procedure
1. Record initial observations for the 6 test substances in Table 1.
2. Place a few crystals of each test substance on a labeled aluminum pan. Arrange them in a
circle on top of the hot plate.
3. Turn on the hot plate. Observe the crystals and note the substance that melts first by
writing a “1” in Table 1. Remove the melted substance immediately. Record the order of
melting, as well as observations of the melting, for each substance in Table 1.
4. After 3 minutes, record an “N” in Table 1 for each substance that did not melt. Remove
the pans, turn off the hot plate, and allow the setup to cool until the lab is complete.
5. Follow the order in Table 1 and put a few crystals of each of the test substances in the
first two columns of your well plate.
6. Add 10 drops of water to each well in the left column. Record the solubility of each
substance without stirring in Table 1.
Ionic vs. Molecular 2
7. Add 10 drops of ethanol to each well in the second column. Record the solubility of each
substance without stirring in Table 1.
8. Test the conductivity of each water solution in the left column by dipping both electrodes
into each well of the well plate. Record the conductivity values in Table 1.
9. Rinse the electrodes with water and dry them. Repeat step 8 for the other test substances.
Data
Compound
Table 1 – Compound Properties
Initial
Solubility in
Melting Point
Observations
H2 O
Solubility in
Ethanol
Conductivity
in Water
Calcium Chloride
(CaCl2)
Citric Acid
Phenyl Salicylate
Potassium Iodide
(KI)
Sodium Chloride
(NaCl)
Sucrose
(C12H22O11)
Questions
1. Group the test substances into two groups according to their properties.
2. List the properties of each group you described in Question 1.
3. Write a statement to summarize the properties of ionic compounds and another statement
to summarize the properties of covalent compounds.
4. If a compound has a high melting point, is soluble in water, and conducts electricity, what
types of bonds do you expect the compound to have? Use an example from the lab to
back up your claim.
Conclusion
Use your knowledge and experimental data to determine which of the groups from Question 1
consists of ionic compounds and which consists of covalent compounds. Was it always clear?
Explain. What are two sources of error in the experiment?